Antibiotic research at the industrial level was originally focused on the identification of refined variants of already existing drugs. This resulted example, in the development of antibiotics such as newer penicillins, cephalosporins, macrolides, and fluoroquinolones.
However, resistance to old and newer antibiotics among bacterial pathogens is evolving rapidly, as exemplified by extended beta-lactamase (ESBL) and quinolone resistant gram-negatives, multi-resistant gonococci, methicillin resistant Staphylococcus aureus (MRSA), vancomycin resistant enterococci (VRE), penicillin non-susceptible pneumococci (PNSP) and macrolide resistant pneumococci and streptococci (see, e.g., Panlilo et al. (1992) Infect. Control Hosp. EpidemioL., 13: 582-586; Morris et al. (1995) Ann Intern Med., 123: 250-259, and the like). An overuse, or improper use, of antibiotics is believed to be of great importance for triggering and spread of drug resistant bacteria. Microbes have, in many cases, adapted and are resistant to antibiotics due to constant exposure and improper use of the drugs.
Drug resistant pathogens represent a major economic burden for health-care systems. For example, postoperative and other nosocomial infections will prolong the need for hospital care and increase antibiotic drug expenses. It is estimated that the annual cost of treating drug resistant infections in the United States is approximately $5 billion.